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On Mon, 2004-09-27 at 15:20, Roberto Nibali wrote:
> Hi,
>
> > I'd like to setup a two node Heartbeat/LVS load balancer using Soekris
> > Net4801 machines. These have a 266Mhz Geode CPU, 3 Ethernet, and 128MB
>
> Horribly slow but for your purpose enough. The limiting factor on those
> boxes are almost always the cache sizes. I've waded through too many
> processor sheets of those Geode derivates to give your specific details
> on your processor but I would be surprised if it had more than 16kb
> i/d-cache each.
>
16k unified cache. :-/
> > of RAM. The OS (probably LEAF) would live on a CF disk.
>
> Make sure that your I/O rate is as low as possible or the first thing to
> blow is your CF disk. I've worked with hundreds of those little boxes in
> all shapes, sizes and configurations. The biggest common mode failures
> were CF disk due to temperature problems and I/O pressure (MTTF was 23
> days); other problems only showed up in really bad NICs locking up half
> of the time.
>
I haven't ever had an actual CF card blow on me. LEAF is made to live on
readonly media.. so its not like it will be written to a lot.
> <sidenote>
> I then did a reliability analysis using the MGL (multiple greek letter,
> derived from the beta-factor model) model to calculate the average risk
> in terms of failure*consequence and we had to refrain from using those
> little nifty things. The costs of repair (detection of failure ->
> replacement of product) at a customer would exceed the income our
> service provided through a mesh of those boxes.
> </sidenote>
>
Not good!
> > If these are
> > overkill, I'd also consider a Net4501, which has a 133Mhz CPU, 64MB RAM,
> > and 3 ethernet.
>
> I'd go with the former ones, just to be sure ;).
>
Forgive me for being frank, but it sounds like you wouldn't go with
either of them.
> > I'd need to balance about 300 HTTP requests per second, totaling about
> > 150kB/sec, between two servers.
>
> So one can assume a typical request to your website is 512 Bytes, which
> is rather quite high. But not really an issue for LVS-DR.
>
I didn't clarify that. The 150kB/sec is outgoing. This isn't for all of
the website, just the static images/html/css.
> > 1) anybody else doing this?
>
> Maybe. Stupid questions: How often did you have to failover and how
> often did it work out of the box?
>
Maybe once every 2 or 3 months I'd need to do some maintenance and
switch to the backup. Every time there was some problem with noarp not
coming up or some weird routing issue with the IPs. Complexity bad. :)
> > 2) IIRC, using the DR method, CPU usage is not a real problem because
> > reply traffic doesn't go through the LVS boxes, but there is some RAM
> > overhead per connection. How much traffic do you guys think these should
> > be able to handle?
>
> This is very difficult to say since these boxes impose limits also
> through their inefficiant PCI busses, their rather broken NICs and the
> dramatically reduced cache. Also it would be interesting to know if
> you're planning on using persistency on your setup.
>
Persistency is not a requirement. Note that most of the time a client
opens a connection once, and keeps it up as long as they're browsing
with keepalives.
> But to give you a number to start with, I would say those boxes should
> be able (given your constraints) to sustain 5Mbit/s of traffic with
> about 2000pps (~350 Bytes/packet) and only consume 30 Mbyte of your
> precious RAM when running without persistency. This is if every packet
> of your 2000pps is a new client requesting a new connection to the LVS
> and will be inserted by the template at an average of 1 Minute.
>
> As mentioned previously, you HW configuration is very hard to compare to
> actual benchmarks, thus take those numbers with a grain of salt, please.
>
Thats not encouraging. I need something fairly cheap.. otherwise I might
as well go down the commercial load balancer route. What do others use
for setups like this? Cheapest 1U's I can find are about $750 USD.
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